Dynamo-electric machine.



ATTbRNEY B. G. LAMME.

- DYNAMO ELECTRIC MACHINE.

APPLIOATION FILED $EPT. 6, l91 0.

BENJAMIN" G. LAMME, 0F PITTSBURGH, PENIIS'X LVANIA, ASSIG-NOR TO W'ES'III-lG-- HOUSE ELECTRIC AND MAI'IUFACTUEING GGMPAIITZ', A GQREORA'Z'ION 0F PENNSYL- VANIA.

nosncoe Sgsecification of .hpp'iicotion filed Sent-ember To all whom 'it may concern: I

Tie it known that l, BENJAMIN LAIA'ME, citizen of the United States, and aresident of Pi tsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Dynamo- Electric Machines, of which the follovvin is a specification.

My invention; relates to dynamo-electric machines and it has special reference to ma chines of the commutator type having mun triple-Wound armatures.

The object of my invention is to provide WGll' proportioned machine of the above indicated class that shall be adapted to on crate satisfactorily under severe operating conditions and shall embod simple and efiective means for increasing the number of commutator bars Without increasing the number ct: armature ampere turns, and fun ther means for obtaining substantially equal voltages between any two adjacent commututor bars at the instant of commutation.

in the design of very high speed or very low voltage machines, it frequent-1y happens thatthe' most suitable number of armature conductors is such as to give too small a number of commutator bars, using one an mature turn per bar. In many cases, in very high speed machines for agiven-output, the

desired voltage can only be obtained, either with a very low inductionper'pole andthe required number of commutator bars, or

with a higher induction per poleond a retors and so few commutator bars,

duced number of armature conductors and commutator bars. It a low induction per pole is chosen, with a relatively large number of armature conductors and. commutator bars, the ampere turns in the armature may become unduly large, so that an abnormally proportioned machine is obtained. On the other hand, if a high induction per pole is chosen, then, even With a multiple wound armature of but a single conduct-or per coil, there may still be so few armature conducth be (i pro cortions are obtained and operating diff culties encountered. For instance: LOG few armatureconductors per circuit, or commutator bars per pole, may lead to pulsations 'commutate unsatisfactorily. such cases,

an arnangement' of armature winding which Letters Patent,

i 1919'. geiial Ii -I0. 580,?63.

would double the number of commutator bars Without doubling the number of armature ampere turns has been found of very considerable advantage.

According to my invention, I employ an armature Winding of the usual multiplewound type, and I provide additional conductors or leads which are-connected to the mid-points of the several armature coils and i are brought through. the slots which lie midway between those that carry the outer c0nductors of the respective coils and are con- .nected to auxiliary commutator bars which are located intermediate the bars to which the outer conductors are connected. Hence, it is manifest, that double the number of commutator bars is obtained, Withoutdoubling the armature ampere turns and also that the potential between adjacent bars Will ,be substantially reduced. However, inasmuch as the middl loads are disposed in the amiature slots and are, therefore, rotated funder the active magnetic field produced by the main field poles, additional means vare provided to rduce the electrocnotive force generated in said conductors at the moment of commutation, so that the existing potential upon intermediate commutator bar shall be approximately half of the potential between the immediately adjacent bars, when said bars are short-circuited by the brushes. 4 y

Hereto'fore, dynamo electric machines have been constructed in which. vthe midpoints of the armature coils have been connected to intermediate commutator bars, but, in such cases, the middle leads have either been disposed inside of the armature core or they have been arranged adjacent to one side of the main coil, so that, during commutation, they did not lie in an active field.

The oarticular advantaces oi m'v invcn-" ciai supports; the number oi. commutator hars are increased Without increasing the number of armature ampere turns; and, the potential between any two ad acent commutator bars is substantially equal, at the moment of commutation, so that oarticularly advantageous commutating conditions are obtained.

Fatented July 2, i932.

- matic development of a portion of an armature winding arranged in accordance with my invention, and Fig. 4 is a view similar to that shown in Fig. 2, with the exception that auxiliary commutating poles are pro} vided intermediate the main field poles.

[Referring to Figsrl, 2 and 3, an armature coil 1 ismounted upon a magnetizable core and is connected to a commutator cylinder 3,'the outer conductors, of said coil being located midway between a plurality of field poles at. The armature coil 1 comprises substantially parallel outer conductors 5 and 6 disposed, respectively, in slots 7 and 8, in the magnetizablecore 2, and connected to commutator bars 9 andllO, respectively. An intermediate lead or conductor 11, which is connected at one end to the main coil lat its mid -p'oint12, isdis'posed within a slot 13 which lies midway between slots 7 and S and is connected, at itsopposite end, to a commu tator bar is intermediate the bars 9 and 10. shown, the coil is in position to be commutated and the commutator bars 9, 10 and- ]4 are bridged by a brush 15.

Since the intermediate conductor 11 is located in a slot in the periphery of the magnetizahle core 2, an electromotive force will at times be generated in it, by reason of its movement through the magnetic fields produced by the main field poles 4. If no such electroinotive force were generated, the

commutator bar let, to which the conductor vi1 is connected, would always lie at a po tcntial midway between those of the two adz acent bars 9 and 10. however, since an electromot-ive force is generated in the conductor 11, when moving through he magnetic field, the intermediate bar 14 is not always maintained at a mid-potential, b tty as this conductor and'the commutator bars 9, 10 and lat carry no current-except when ,short-circuitcd by a brush, it is not impor tant that a midway potential be maintanied upon the bar 14,, except at the time of commutation. I

It will be observed that, at the time of commutation, the intermediate conductor'll lies under the middle of a field pole e and,

therefore, is generating an electromotive torcewhen the two sides 5 and .6 otithe' coil 1 are passing through the neutralo'ri interpolar spaces 16 and 17, respectively.

It is at just this time that the intermediate conductor should generate the least voltage. The sideconductor 8 and the intermediate conductor 11 may be considered'as a halfcoilv which is commutated first, while the other side conductor 5 and the intermediaxe,v conductor 1 may be considered as a second halt-coil which is commutated immediately afterward. Inasmuch as this conductor cuts the active magnetic field, .it has generated in it an electromotive force which assists commutation and-reversal of current for one of these half-coils, and opposes the reversal in the remaining half coil, as will be readily understood. It is, therefore, desirable to reduce this electromotivetorce to as low a value as possible, in order to prevent the opposing action in commutating one or the other of said half-coils; In order to overcome this difiiculty, I propose to cut a notch 35 or slotQO inthe middle of each of the main field pole pieces to correspond to the positions oft-he intermediate conductor at the instant of commutation, By this means, a

great reduction in strength of the magnetic field underthe middle of the pole faces is obtained, so that the intermediate conductors generate but very small electromotive forces at this instant, and hence, satisfactory com,- mutation may be secured. This electromotive force, however, can not well be reduced to 'Zero value, as it is impracticable, in most cases, to obtain a zero magnetic field under the center of the main field poles. It is evident, therefore, that a weak magneticfield is obtained directly over the intermediate conductor 11 at the moment of commutation. lrlence, only a very small voltage is generated therein and, consequently, good commu tation may be efiected.

Those skilled in the art- Will readily under stand that, since the polarity of the magnetic field is the same at both edges of the polar notches 20, shown in Fig. 2, that the magnetic fringing'into the armature under said notches is such as to add to one another atall positions, so that there is no position under said polar notches which has zero field and, hence, a very slight -elect-romqtive force is generated. In most cases, the reduction in magnetic field under the middle of the ,';pole faces is sufliciently low to secure good commutation. However, oases may arise in which a further reduction inflthe electromotive force than is'practicable to secure by. means of polar notches, may be obtained by the use of commutating poles of suitable proportions. p

In Fig. 4, commutating poles 23 areprovided between the mainfield poles a. The other parts of the drawing are similar to those shown in Fig.2 and bear like reference numerals. V

It will be evident to those skilled in the art that the efiect of any slightelectromw tire forces generated in the intermediate con project-ions at the time of commutation.

-midway hetwecn the respective side conduca. plurality of bars and. a of coiiperctors under the polar notches 2:), at the oment of commutation, may he eliminated hr a proper design or connimtaling poles, so that good conunutation may be secured under the most adrerse opci ting conditions.

I desire that my invention shall not be limited to the arrangement rad structural details shown and described; that modifications which do not depart from the spirit; c 1 my inrention shall he int'sludcd within its scope; and that only such limitations shall be imposed as are indicated in the appein ed claims.

I claim as my invention:

1. ln a dynamo-electric machine, the comhination with a field magnet having polar projections provided with centrally disposed face slots, a magnetizahle core having a plurality of slots, and a commutator cylinder comprising a plurality of bars, of an arma ture winding comprising a plurality of coils' disposed in said slots, the side conductors 01'? which are connected to alternate eoi'nmutator bars, and an intermediate conductor for each coil disposed in a slot approximately midway between the respective side conduc tors and connected atone. end to the midpoint of said coil and at the other end to a cianmutator bar intermediate the bars to which the side conductors of said coil are connected, said intermediate conductors being directly beneath the slots in the polar 2. In a dynaino-elcctric machine the coinhination with a magnetizahle core having a plurality of slots, a conunutator cylinder comprising a plurality of bars, and an armature winding comprising a plurality of coils disposed in said slots, each, coil comprising two side conductors connected, to alternate commutator hats, and an intermediate conduct'or disposed in a f ot approximately tors and connected at one end lc the mi point of said coil and at the other to a commutator har intermediate the bars which the side conductors are conncctwl, and a hold magnet provided with means tor obtaining a potential on each intermediate har which is substantially one half of the ential between the two innnediately any at the. instant of commutation.

ln a dynamo clectric machine, the combination with a magnetizable corehaving a plurality of slots, a connuntator comprising siting brushes, and an armature winding comprising separate coils disposed in said slots, each torzned of three equally spaced parallel conductors, the outer conductors he i ing connected, at their extremities, Lo-alterate commutator bars and the int 'niediate conductor hemp; connected to an intermediconductor connected to separate commutator bars, of a field magnet provided with means for reducing the influence 01" said poles upon said intermediate COHClUCtOl'S when the coils are short- CllCUlt((l hy the brushes.

In a dynamo-electric machine, the com- -hination with a inagnctizahle core having a plurality of slots, a. connnutator cylinder comprising a plurality of bars, and an armature winding comprising a plurality of coils, each formed of three parallel equally spaced conductors disposed in separate slots and connected to separate commutator bars, ota field magnet having a plurality of polar projections, slots parallel to the armature core slots and located in the middle of the respective pole faces, and a plurality of coinmutating poles intermediate said polar projections.

(3. In a dynamo-electric machine, the combination with a field magnet having a plurality of pole pieces, a magnctizahle core having; a plurality of slots, a commutato'r comprising a plurality of bars and a of brushes to coiiperate therewith, of an armature winding conmrising a plurality of son aratc coils disposed in said slots, each coil con'iprising two outer condiuztors connected to alternate commutator hars'and an intermediate conductor located midway between said outer conductors and connected to an. intermediate connnutator ha the pitch each coil being such that its outer conductors lie midway between the ticld magnet polo. pieces at: the moment; it: is short-circuited by the brushes, being provided with notches that; are located midway between the pole tips and parallel to the armature core slots.

In testimony whereof, l have hereunto subscribed my name this 18th cay of August, 1910.

BENJ. G. Lnlliiill l.

Witnesses:

C. W. MoGnnn, R. J. DEARRORN.

and the field magnet pole pieces 7 

